Mixtures of olefin polymers and nitrile rubbers

ABSTRACT

This invention relates to a mixture containing one or more olefin rubbers and one or more nitrile rubbers, to a process for the production thereof, to a vulcanizable mixture and to a process for the production thereof as well as to moldings of all kinds producible from the mixtures.

FIELD OF THE INVENTION

[0001] This invention relates to a mixture containing one or more olefinrubbers and one or more nitrile rubbers, to a process for the productionthereof, to a vulcanizable mixture and to a process for the productionthereof as well as to moldings of all kinds producible from themixtures.

BACKGROUND OF THE INVENTION

[0002] Mixtures (blends) of incompatible elastomers are frequentlyencountered in industrial rubber articles. In general, the polymercomponents are mixed in a single mixing operation together withconventional additives without any particular measures being implementedto improve phase structure.

[0003] It is often observed in such processes that the expectedimprovements in certain material properties are accompanied byconsiderable disadvantages in other properties which are the result ofinsufficiently uniform distribution of the polymer phases in the blends.Mixtures containing EPDM may be taken by way of example. In mixtureswith nitrile rubber (NBR), EPDM primarily improves low temperatureflexibility. In contrast, other properties, such as vulcanizate strengthand oil swelling, are impaired.

[0004] Improved mixing processes provide complicated, often multistageprocesses which are time-consuming and entail excessive mixing costs.

[0005] Mixtures of olefin polymers with nitrile rubbers are known, forexample, from EP-A2-0 146 068, EP-A1-0 773 255 and U.S. Pat. No.3,492,370. Although, macroscopically, these mixtures appear homogeneous,extensive domains of disperse phases are clearly evident on examinationby phase-contrast microscopy (FIG. 1).

SUMMARY OF THE INVENTION

[0006] Therefore, the object of the present invention is to provide amixture of olefin rubber and nitrile rubber having improved properties.

[0007] This object is achieved by a mixture containing one or moreolefin rubbers and one or more nitrile rubbers, characterized in thatthere is no phase segregation in the mixture.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 shows the phase distribution in a mixture according to theprior art;

[0009]FIGS. 2 and 3 show the improvement achieved by the processaccording to the present invention.

[0010]FIG. 4 shows a diagrammatic representation of mixture productionin GK 90 E internal mixer

DETAILED DESCRIPTION OF THE INVENTION

[0011] For the purposes of the present invention, olefin rubber is takento mean copolymers prepared from ethylene and one or more α-olefins,terpolymers prepared from ethylene, one or more α-olefins and one ormore unconjugated dienes, as well as mixtures of polymers containing thestated polymers.

[0012] The α-olefins are here in particular selected from the group ofpropylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and1-nonene, very particularly propylene, 1-butene, 1-hexene and 1-octene.

[0013] The unconjugated dienes are selected from the group of1,4-hexadiene, 1,5-heptadiene, 5,7-dimethyl-1,6-octadiene,7-methyl-1,6-octadiene, 4-vinyl-1-cyclohexene,5-ethylidene-2-norbornene, 5-vinyl-2-norbornene and dicyclopentadiene,preferably 1,4-hexadiene, 7-methyl-1,6-octadiene,5-ethylidene-2-norbornene, 5-vinyl-2-norbornene and dicyclopentadiene.

[0014] Suitable olefin rubbers generally have Mooney viscosities (DIN 53523, ML 1+4, 125° C.) of 20 to 100 MU, in particular of 25 to 80 MU,wherein it is, however, also possible to use liquid olefin rubbers, inparticular liquid EP(D)M rubbers.

[0015] Nitrile rubbers are diene/(meth)acrylonitrile copolymers.Isoprene and, in particular, butadiene are preferred dienes. Thecopolymers have a content of copolymerized acrylonitrile and/ormethacrylonitrile units of 5 to 60, preferably of 10 to 50 wt. %.

[0016] Furthermore, hydrogenated nitrile rubbers are explicitly includedin the class of nitrile rubbers. For the purposes of this invention,“hydrogenated nitrile rubber” or “HNBR” should be taken to mean nitrilerubbers, the C═C double bonds of which are partially or completelyhydrogenated in a selective manner (i.e. without hydrogenation of theC≡N triple bond). Preferred hydrogenated nitrile rubbers are thosehaving a degree of hydrogenation, relative to the C═C double bondsoriginating from the butadiene, of at least 75, preferably of at least90, in particular of at least 95%. The degree of hydrogenation may bedetermined by NMR and IR spectroscopy.

[0017] The hydrogenation of nitrile rubber is known from U.S. Pat. No.3,700,637, DE-A-2 539 132, DE-A-3 046 008, DE-A-3 046 251, DE-A-3 227650, DE-A-3 329 974, EP-A1-0 111 412 and FR-B-2 540 503, wherein thestated documents are hereby incorporated into the present application asa reference for the purposes of US patent practice. Hydrogenated nitrilerubber is characterized by elevated tear strength, low abrasion, slightresidual deformation after exposure to compressive and tensile stressesand good oil resistance, but in particular by remarkable resistance tothermal and oxidative exposure. Hydrogenated nitrile rubbers areaccordingly preferred for the purposes of the invention.

[0018] Suitable nitrile rubbers generally have Mooney viscosities (DIN53 523, ML 1+4, 100° C.) of 25 to 120 MU, in particular of 40 to 100 MU,wherein it may, however, also be advantageous to use liquid nitrilerubbers.

[0019] For the purposes of the invention, phase segregation is taken tomean that the domains of the disperse phases have an average diameter ofless than 10 μm. It should be noted in this connection that the phasesdo not comprise spherical structures, but instead irregular structureswith indentations and protruberances (c.f. FIG. 1-3), such that thediameter should in each case be measured at the narrowest point.However, it is frequently possible to make an initial assessmentvisually by phase-contrast microscopy. The difference between themixtures according to the present invention and the prior art is thussignificant from a comparison of FIGS. 1-3 (FIG. 1 in comparison withFIGS. 2 and 3).

[0020] The average diameters of the domains of the disperse phases arepreferably less than 5 μm.

[0021] The present application also provides a process for theproduction of a mixture containing one or more olefin rubbers and one ormore nitrile rubbers, characterized in that, before or during productionof the mixture, small quantities of a vulcanizing system which is activeat the mixing temperature, in particular a peroxide system having adecomposition temperature below the mixing temperature, are added.

[0022] Usable mixing units comprise any mixing units for rubbers knownto the person skilled in the art, in particular kneaders, roll mills andextruders.

[0023] The Mooney value of the mixture rises during the mixing process.The necessary quantity of vulcanizing agent, in particular peroxide, isdependent upon the intended purpose of the mixture and the desiredincrease in Mooney value, but may readily be determined by somepreliminary testing. Complete vulcanization of the mixtures should,however, not occur at this point. As stated, it is known that thequantity of vulcanizing agent required is indirectly proportional to theresidual double bond content of the rubber.

[0024] The aim of the mixing process is to produce the mixture in such amanner that greater than 90, preferably greater than 95 wt. %, relativeto rubber, may be extracted by 10 hours' extraction in a Soxhletapparatus with toluene or a solvent from the group consisting ofdichlorobenzene, methyl ethyl ketone or mixtures thereof as theextracting agent. The mixture should, thus, not be completelyvulcanized.

[0025] For the purposes of the invention, vulcanization means that lessthan 10, preferably less than 5 wt. %, relative to rubber, may beextracted by 10 hours' extraction in a Soxhlet apparatus with toluene asthe extracting agent.

[0026] It is vital to the invention that the vulcanizing agent is activeat or below the mixing temperature, i.e. it initiates vulcanization. Inthe case of peroxides, it is thus vital that the decompositiontemperature of the peroxide system is below the mixing temperature.Depending upon the mixing temperature, the following are examples ofperoxides which are suitable for the process according to the presentinvention:

[0027] bis-(2,4-dichlorobenzyl) peroxide

[0028] dibenzoyl peroxide

[0029] bis(4-chlorobenzoyl) peroxide

[0030] 1,1 -bis(t.-butylperoxy)-3,3,5-trimethylcyclohexane

[0031] tert.-butyl perbenzoate

[0032] 2,2-bis-(t.-butylperoxy)butene

[0033] 4,4-di-tert.-butyl peroxynonylvalerate

[0034] 2,5-dimethyl-2,5-di(tert.-butylperoxy)hexane.

[0035] Since it is advantageous to perform mixing at below 190° C.,2,5-dimethyl-2,5-di(tert.-butylperoxy)hexane is preferred.

[0036] The quantities of peroxide are generally in the range from 0.2 to5 phr, preferably in the range from 0.5 to 3 phr, relative to rubber.

[0037] The peroxides may advantageously also be used in polymer-boundform.

[0038] Further suitable vulcanizing agents are sulfur or sulfur donorsas well as combinations of these components.

[0039] Sulfur may be used as soluble or insoluble sulfur, as a mixturethereof (pulverulent, coated) or in another suitable form, for exampleas a premixed mixture of sulfur and rubber or “sulfur batch”. The rateof addition is generally in the range from 0.1 to 5 phr, preferably 0.1to 1.5 phr.

[0040] Sulfur donors which may in general be considered are derivativesof thiuram, in particular tetramethylthiuram disulfide,tetraethylthiuram disulfide, tetrabutylthiuram disulfide andtetrabenzylthiuram disulfide. These may in turn be used in combinationwith other components containing sulfur, for example dithiomorpholide,dithiocaprolactam or other compounds having a di-, tri-, tetra- orpolysulfide structure.

[0041] The rate of addition of the thiuram derivatives is conventionallyin the range from 0.5 to 5 phr, preferably 1 to 2.5 phr. The rate ofaddition of the complementary components containing sulfur shouldgenerally be selected in the range from 0.1 to 3 phr, preferably from0.5 to 1.5 phr.

[0042] Sulfur vulcanizing systems may moreover contain accelerators.Accelerators which are preferably considered are those of themercaptobenzothiazole or mercaptobenzothiazyl disulfide type at rates ofaddition generally in the range from 0.5 to 3 phr, preferably from 0.5to 1.5 phr or so-called sulfenamides, such as for examplecyclo-hexylbenzolthiazylsulfenamide (CBS),tert.-butylbenzothiazylsulfenamide (TBBS), morpholinebenzothiazylsulfenamide (MBS), dibenzylbenzo-thiazyl-sulfenamide (DCBS),wherein these are conventionally used at rates of addition in the rangefrom 0.5 to 3, preferably from 0.5 to 1.5 phr.

[0043] It may, furthermore, be advantageous to use the followingadditives:

[0044] zinc salts of dithiocarbamic acids at rates of addition in therange from 0.5 to 1.5 phr,

[0045] derivatives of dithiophosphoric acid, guanidines and other amineaccelerators conventional in the rubber industry,

[0046] retarders, such as phthalic acid, phthalic anhydride, benzoicacid or salicylic acid or other organic acids, such as N-nitrosocompounds or such as N-cyclohexylthiophthalimide or other sulfonamidederivatives, such as Vulkalent E/C from Bayer AG.

[0047] Any combination of vulcanizing agents and accelerators generallyrequires activators, preferably zinc oxide and fatty acids. The rate ofaddition of zinc oxides is conventionally in the range from 2 to 15 phr,preferably from 3 to 5 phr. One suitable fatty acid is, for example,stearic acid, which is generally used at rates of addition in the rangefrom 0.1 to 2 phr, preferably from 0.3 to 1 phr.

[0048] Mixing generally proceeds at temperatures in the range from 150to 200° C., preferably from 160 to 190° C., optionally under a pressureof 10 to 200 bar. After mixing, the mixtures may be post-cured by beingkept at elevated temperature.

[0049] Especially when the volume being mixed is large, it is oftenadvantageous to produce a homogeneous mixture of rubber and vulcanizingagent at low temperatures and then to increase the mixing temperature.

[0050] The mixtures according to the present invention may, moreover,contain conventional additives.

[0051] Additives which may be considered are, for example, thevulcanization activators known to the person skilled in the art, inparticular, metal oxides, such as zinc oxide or magnesium oxide,antioxidants, such as alkyl-substituted diphenylamines,mercaptobenzimidazoles, unsaturated ethers, such as Vulkazon® AFD (BayerAG, Germany), or cyclic, unsaturated acetals, such as Vulkazon® AFS/LG(Bayer AG, Germany). Other additives which may be mentioned are:

[0052] plasticizers, in particular carboxylic acid esters, such assebacic acid and the derivatives thereof or trimellitic acid and thederivatives thereof

[0053] processing auxiliaries, in particular stearic acid and thederivatives thereof, such as zinc stearate or polymers, such aspoly(ethylene/vinyl acetate) (Levapren® from Bayer AG, Germany) orpoly(ethylene/vinyl acrylate) (VAMAC® from DuPont).

[0054] It may, furthermore, be advantageous to incorporate fillers intothe rubber mixture according to the present invention. These may or maynot have a reinforcing action.

[0055] Fillers which may, for example, be mentioned are:

[0056] carbon blacks, such as MT, GPF, SRF and especially FEF blacks,

[0057] metal oxides, such as titanium dioxide (especially as a whitepigment)

[0058] silicates, such as sodium aluminium silicate

[0059] silicas, preferably precipitated silicas So-called active fillersin accordance with proposal ISO 5794, appendix D, part 1, for examplepublished on page 535 of “Handbuch für die Gummiindustrie” from BayerAG, 1992, Leverkusen are preferably suitable for improving abrasionproperties.

[0060] clays, mica, talcum.

[0061] It may, additionally, be advantageous to use additionalactivators for improving adhesion between filler and rubber, such as forexample silanes, such as Ucarsil® RC-1 (Union Carbide, US). Pigmentsmay, furthermore, be added.

[0062] The quantities of the individual mixture components depend uponthe intended purpose of the mixture and may be determined by somepreliminary testing.

[0063] As a rule, the additives (substantially additives and fillers)are used in the following quantities (in each case in phr=parts perhundred parts of rubber):

[0064] antioxidants in the range from 0 to 4 phr,

[0065] retarders in the range from 0 to 2 phr,

[0066] metal oxides, such as ZnO, in the range from 0 to 30 phr,

[0067] fillers in the range from 0 to 150 phr, preferably activefillers,

[0068] plasticizers in the range from 0 to 20 phr,

[0069] processing auxiliaries in the range from 0 to 2 phr.

[0070] It is a routine matter for the person skilled in the art totailor the properties of the mixtures according to the present inventionto the exact requirements by adding further polymers, such as BR, NR,IIR, IR, CR, SBR, AEM, ACM or fluoropolymers.

[0071] The additives and fillers are incorporated by mixing operations.Care must be taken in this respect that the mixture is not degradedduring the mixing operation. It may accordingly be advantageous toprovide cooling during the mixing operation.

[0072] The resultant mixtures may be further blended with vulcanizingagents, in order to obtain vulcanizable mixtures which are thenultimately converted into moldings of all kinds.

[0073] These vulcanizing agents are in general always added whenvulcanization is not to be performed with high-energy radiation. Theabove-stated vulcanizing systems and components are suitable for thispurpose, as are also any further vulcanizing agents known to the personskilled in the art which become active only above the mixing temperaturein the process according to the present invention; peroxides having adecomposition temperature above the mixing temperature in the processaccording to the present invention are explicitly also mentioned in thisconnection.

[0074] Depending upon the intended purpose, in addition to the statedperoxides, the following peroxides are, for example, suitable:

[0075] dialkyl peroxides,

[0076] ketal peroxides,

[0077] aralkyl peroxides,

[0078] peroxide ethers,

[0079] peroxide esters, such as for example

[0080] di-tert.-butyl peroxide,

[0081] bis(tert.-butylperoxyisopropyl)benzene,

[0082] dicumyl peroxide,

[0083] 2,5-dimethyl-2,5-di(tert.-butylperoxy)hexane,

[0084] 2,5-dimethyl-2,5-di(tert.-butylperoxy)-3-hexene,

[0085] 2,5-dimethyl-2,5-di(tert.-butylperoxy)hexyne,

[0086] 1,1-bis(tert.-butylperoxy)-3,3,5-trimethylcyclohexane,

[0087] benzoyl peroxide,

[0088] tert.-butylcumyl peroxide and

[0089] tert.-butyl perbenzoate.

[0090] In order to avoid scorching, the vulcanizing system is in thiscase often added as the final component, optionally in a separate mixingoperation.

[0091] Further suitable vulcanizing agents are sulfur or sulfur donorstogether with combinations of these components, which have already beendescribed.

[0092] Unsurprisingly, the mixtures produced by the process according tothe present invention are indistinguishable by DSC measurements fromconventionally produced mixtures. It may, however, be proven by GPCanalysis that primarily the olefin rubber phase, but probably also,although to a lesser degree, the nitrile rubber phase, has undergonestructural modification.

[0093] In mixtures with and without vulcanizing agents, an at leastbimodal elution diagram is obtained, which is determined by the narrowerdistribution of the olefin rubber in the range of lower molecularweights and by the wide nitrile rubber distribution in the range ofelevated molecular weight distribution.

[0094] However, the reaction in the process according to the presentinvention gives rise to a modified mixture. The range of lower molecularweights determined by the olefin rubber is widened and the contentthereof of fractions with a molecular weight of below 5×10⁵ g/mol isreduced.

[0095] The most important result is the improvement in phasedistribution, evident from microscopic examination, of the polymercomponents, as shown in FIG. 1-3. FIG. 1 shows the phase distribution ina mixture according to the prior art, while FIGS. 2 and 3 show theimprovement achieved by the process according to the present invention.

[0096] In comparison with moldings made from conventionally producedmixtures, the moldings produced from these mixtures are generallycharacterized by improved mechanical properties and by better resistancein mineral oils.

[0097] Moldings are taken to mean not only moldings in the conventionalsense, such as profiles, belts, rings, seals, damping elements, but alsocoatings, coverings and other flat or three-dimensional structures.

[0098] Further moldings primarily used in oil extraction are:

[0099] seals of various designs on drill pipes, suspension gear andtubes, such as for example O rings and lip seals, individually or aspackings,

[0100] packer seals and the like,

[0101] adjusting elements, spacers, protectors and resilient bearings(also inflatable) for drill pipes, suspension gear, tubes and equipment,

[0102] seals and inserts for blow out preventers,

[0103] seals, membranes and balls for control valves and similardevices,

[0104] seals, membranes and bubbles for pulse dampers and the like,

[0105] closing bungs,

[0106] seals, membranes, rotors (impellers) and stators for pumps,

[0107] bungs and seals for pipe cleaning,

[0108] reinforced and unreinforced hoses, floating hoses,

[0109] cable insulation and sheathing.

[0110] Especially for coatings, it may be advantageous to improverubber/substrate adhesion by adhesion promoters such asdispersions/solutions of halogenated polymers, optionally comprisingvulcanizing agents/fillers/pigments. These substances are commerciallyavailable and are described, for example, in EP-A2-0 252 264, which ishereby incorporated into the present application as a reference for thepurposes of US patent practice.

[0111] The following Examples illustrate the invention, without therebeing any intention to restrict it.

EXAMPLES

[0112] Measurement methods Residual double bond content IR spectroscopyMooney viscosity ASTM D 1646 (stated in MU) Volatile constituents (wt.%) ASTM D 1416 Ash content (wt. %) ASTM D 1416 Acrylonitrile (ACN)content in accordance with the following method: (wt. %, polymer bound)

[0113] Brief description of process for determining ACN content

[0114] For the purposes of the analysis, the rubber is pyrolyzed on acatalyst at 900° C. in a stream of oxygen. The unconsumed oxygen isabsorbed in a copper reduction reactor and the resultant NO—X gases arereduced to nitrogen. An Na₂CO₃/NaOH trap is then used to remove the CO₂present in the gas stream under analysis and an MgCIO₄ trap to removethe water. The change in thermal conductivity of the gas under analysisin comparison with the carrier gas stream is a measure of the nitrogencontent of the sample.

[0115] Equipment for the process

[0116] Protein analyser, from Fisons, model NA 2000

[0117] Microbalance, from Sartorius, Micro model

[0118] Evaluation unit, from Digital, model DECpc Lpd 433 dx withinterface to NA 200 and balance interface, together with EAGER 200software

[0119] Chemicals and solvents for the process

[0120] Methionine, from Hekatech Formulation constituents Therban ® C3467 Bayer AG HNBR with 5.5% RDB, 34% ACN, 68 MU (ML(1 + 4) 100° C.)Therban ® C 3446 Bayer AG HNBR with 2.9-5.0% RDB, 34% ACN, 58 MU (ML(1 +4) 100° C.) Buna ® EP G 3440 Bayer AG EPDM with 48% ethylene, 4.1% ENB,28 MU (ML(1 + 4) 125° C.) Zinkoxyd ®, active Bayer AG active zinc oxideScorchguard ® O Rhein Chemie magnesium oxide paste Rheinau GmbH Naugard445 Uniroyal substituted diphenylamine Vulkanox ® ZMB 2 Bayer AG zincmethylmercapto- benzimidazole Rhenocure ® M Rhein Chemiedithio-bis-morpholine Rheinau GmbH Edenor HTIG Henkel KGaA stearic acidDiplast TM 8-10/ST Lonza SpA, Italy trioctyl mellitate Carbon black N772Columbina Carbon Carbon black N550 Degussa-Hüls AG Vulkacit ® thiuramBayer AG tetramethylthiuram disulfide Vulkacit ® CZ Bayer AGN-cyclohexyl-2-benzo- thiazylsulfenamide Perkalink 301 Flexsys AGtriallyl cyanurate Trigonox 29/40 AkzoNobel N.V.1,1-bis(t.-butylperoxy)- 3,3,5-trimethylcyclohexane, 40% activesubstance

Example 1

[0121] A mixture of the following composition is produced in alaboratory internal mixer, GK 1.5 E (manufacturer: KruppElastomertechnik):

[0122] Therban® C 3446: 70 wt. %

[0123] Buna® EP G 3440: 30 wt. %

[0124] Trigonox 29/40: 2 wt. %

[0125] The mixture is produced under the following conditions: Coolingwater temperature: 80° C. Rotor speed: 70 rpm Plunger pressure: 6 barFilling level: 78%

[0126] The polymeric components are initially introduced, the peroxideis added after 1 minute and the temperature rises to above 150° C.within a further 2.5 minutes. After a total mixing time of 3.5 minutes,the mixture is discharged. Despite the addition of peroxide, the mixtureis plastic.

[0127] In comparison with an identical mixture produced without addedperoxide, the following properties are measured: Mixture with peroxideMixture without peroxide ML 1 + 4/100° C. 120 70 (MU)

[0128] (Determined to ASTM D 1646. In accordance with the instructionsin the standard, the mixture sheets are pretreated in a roll mill beforemeasurement).

[0129] The mixtures with peroxide exhibit distinctly improved phasestructures (method: phase-contrast microscopy)

[0130]FIG. 1 without peroxide: phase segregation

[0131]FIG. 2 with peroxide: no phase segregation

[0132] It may furthermore be observed that the mixture according to thepresent invention exhibits a distinctly higher Mooney viscosity, whichwould indicate that a reaction has occurred during mixing.

[0133] These mixtures are the polymeric base for mixtures of thefollowing composition: TABLE 1 Test formulations Peroxide vulcanizationSulfur vulcanization HNBR/EPDM blend 100 100 Edenor HTIG 1 Zinkoxyd,active 2 5 Scorchguard O 2 Carbon black N 772 65 Carbon black N 550 50Diplast TM 8-10/ST 5 5 Vulkanox ZMB2 0.4 Naugard 445 0.5 Perkalink 3011.5 Dicumyl peroxide (40%) 5 Rhenocure M 1.1 Vulkacit thiuram 1.1 Sulfur0.5 Vulkacit CZ 0.8

[0134] This mixture is produced in a further mixing step in the samemixing unit.

[0135] The mixing conditions for this purpose are selected in theconventional manner, namely: Mixer GK 1.5 E Chamber/blade temperature50° C. Plunger pressure 8 bar Rotational speed 40 rpm Filling level 70%

[0136] Mixing cycle:

[0137] Introduce polymer and

[0138] mix for 60 seconds

[0139] add fillers, chemicals, plasticizer and

[0140] mix for 90 seconds

[0141] sweep

[0142] mix for 60 seconds or up to a max. of 145° C.

[0143] discharge

[0144] place cleaning chemicals on the roll.

[0145] Once discharged, the mixture is vulcanized at 170° C./30 minutes.The following properties are determined on sample sheets in accordancewith standards (essentially DIN 53 504). TABLE 2 Properties of themixtures Mixture without Mixture with peroxide peroxide Strength (MPa)15 20 (DIN 53 504) Elongation at break 305 280 (DIN 53 504) Modulus(100% 4.4 5.8 elongation) (MPa) (DIN 53 504) Shore A hardness 68 71 (DIN53 505) Immersion in standard oil IRM 903, 3d/135° C. Change in volume96% 60%

Example 2

[0146] In internal mixers with a capacity suitable for industrialproduction, the process and formulation must be modified as the peroxideis distributed less rapidly and localized inhomogeneities give rise toundesirably high levels of vulcanization at these points, resulting in anegative impact upon the processability of the final product.

[0147] This step is illustrated by making the transfer from the GK 1.5 Einternal mixer described above to a GK 90 E internal mixer, both ofwhich have an intermeshing rotor geometry.

[0148] The external mixing conditions had to be adapted as follows:TABLE 3 Mixing conditions, comparison of GK 1.5 E and GK 90 E GK 1.5E GK90E Temperature ° C. 80 80 Rotor speed rpm 70 20 rpm, then 70 rpmPlunger bar 6 8 pressure Filling level % 78* 73**

[0149] It is essential to provide variable motor speeds with aninitially low rotational speed (20 rpm) and slight evolution oftemperature in order to ensure homogeneous dispersion of the peroxideand then to increase the rotational speed in order to generate thetemperature necessary for the reaction.

[0150] On this basis, production of the mixture in the GK 90 E internalmixer proceeds in accordance with the following diagrammaticrepresentation (FIG. 4).

[0151]FIG. 4: Diagrammatic representation of mixture production in GK 90E internal mixer

[0152] At the low rotational speed, the temperature of the compositionremains below 120° C. Under these conditions, the peroxide undergoesvirtually no decomposition for this period of mixing, but is insteadonly dispersed. As soon as the speed is raised to 70 rpm, thetemperatures of approx. 190° C. required for the coupling reaction areachieved within the following 4 minutes.

[0153] The rate of peroxide addition suitable for this purpose wasdetermined from the following preliminary tests and, in the presentcase, was set at 1 phr, as good processability may still be anticipatedat 80-90 MU (Table 4): TABLE 4 Influence of rate of peroxide additionupon Mooney viscosity of mixture in GK 90 E internal mixer Test no. A BC D Therban ® C 3446 70 70 70 70 Buna ® EP G 3440 30 30 30 30 Trigonox29/40 0 0.5 1 1.5 Mixing temperature 184 183 185 186 (° C.) ML 1 +4/100° C. (MU) 49 66 88 110

[0154] Batch-off treatment of the mixture with peroxide proceededwithout problems. The mixture sheet was plastic. There were noobservable signs of scorching.

[0155] Although the invention has been described in detail in theforegoing for the purpose of illustration, it is to be understood thatsuch detail is solely for that purpose and that variations can be madetherein by those skilled in the art without departing from the spiritand scope of the invention except as it may be limited by the claims.

What is claimed is:
 1. A rubber mixture comprising one or more olefinrubbers and one or more nitrile rubbers, wherein there is no phasesegregation in the mixture.
 2. A rubber mixture according to claim 1,wherein said one more nitrile rubber(s) are selected from the groupconsisting of NBR, partially hydrogenated NBR, completely hydrogenatedNBR or mixtures of two or more of the members of the group.
 3. A rubbermixture according to claim 1, wherein the olefin rubber(s) are selectedfrom the group of copolymers prepared from ethylene and one or moreα-olefins, terpolymers prepared from ethylene, one or more α-olefins andone or more unconjugated dienes, as well as mixtures of polymerscontaining the stated polymers.
 4. A rubber mixture according to claim1, wherein the mixture comprises one or more additives and/or fillers.5. A rubber according to claim 1, wherein the mixture is more than 95%soluble in organic solvents selected from the group consisting ofdichlorobenzene, methyl ethyl ketone or mixtures thereof.
 6. Avulcanizable rubber mixture comprising a mixture, which comprises one ormore olefin rubbers and one or more nitrile rubbers, wherein there is nophase segregation in the mixture.
 7. A rubber mixture according to claim6, wherein the vulcanizing agent is selected from the group consistingof peroxide, sulfur, thiuram or a mixture of two or more of thesecomponents.
 8. A rubber mixture according to claim 6, wherein themixture comprises vulcanization retarders and/or vulcanizationaccelerators.
 9. A process for the production of a mixture according toclaim 7, wherein the components are mixed in a mixing unit.
 10. Aprocess according to claim 9, wherein the mixture is cooled during themixing operation.
 11. A process for the production of a mixturecomprising one or more olefin rubbers and one or more nitrile rubbers,wherein, before or during production of the mixture, small quantities ofa vulcanizing agent which is active at the mixing temperature, areadded.
 12. A process according to claim 11, wherein one or moreperoxides having a decomposition temperature below the mixingtemperature is/are added as the vulcanizing agent.
 13. A processaccording to claim 11, wherein the mixing temperature is in the rangefrom 150° C. to 200° C.
 14. A process according to claim 11, wherein theperoxide content is in the range from 0.05 to 4 phr.
 15. A process forthe production of a mixture according to claim 11, wherein thecomponents are mixed in a mixing unit.
 16. Moldings comprising a rubbermixture, which comprises one or more olefin rubbers and one or morenitrile rubbers, wherein there is no phase segregation in the mixture.